First responders attend to injured passengers after a Cardinal Coach Line charter bus flipped on its side on northbound SH 161 near Belt Line Rd. in Irving, Texas, Thursday, April 11, 2013. At least two people were killed and more than 40 were hospitalized after a charter bus careened off a North Texas highway and flipped onto its side Thursday, drawing a large emergency response as rescue crews struggled to reach victims inside, authorities said. (AP Photo/The Dallas Morning News, Tom Fox)

DALLAS (AP) — More than a dozen people remain hospitalized after a bus veered off a North Texas highway, struck a concrete barrier and toppled over in an accident that killed two people.

More than 40 people were injured in the wreck Thursday in Irving. Most of the 19 still hospitalized Friday morning are being treated at Parkland Memorial Hospital in Dallas.

Sixty-nine-year-old Paula Hahn of Fort Worth, and 81-year-old Sue Taylor of Hurst, a Fort Worth suburb, were killed in the accident.

State and federal authorities are investigating what caused the Cardinal Coach Line bus to career across the highway and into the center median. Some 45 passengers were aboard, senior citizens on their way to an Oklahoma casino.

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